It started right in front of a cave with a guy shelling you things. You progress through caves to an underground city, from there you have access to other caves. In the city you get missions ala Borderlands.
It was a post-apocaliptic theme with mutant enemies (rats, worms, maybe humans, etc). You got an inventory with different sizes for different items (like Deus Ex) and i think you could craft weapons with pieces.
It had Deux Ex mechanics, with more exploration and searching for objects than action, but it was mainly a shooter, with weapon on screen.
I belive it was russian language only but i'm not sure. It probably came out before STALKER, 2000-2007.
Thanks!